Method for preparing halogenated maleic acid, salts and anhydrides thereof



United States Patent METHOD FOR PREPARING HALOGENATED MALEIC ACID, SALTS AND ANHYDRIDES THEREOF Charles J. Pennino, Hudson, Ohio, assignor to The B. F. Goodrich Company, New York, N. Y., a corporation of New York No Drawing. Application February 1, 1955 Serial No. 485,589

9 Claims. (Cl. 260--346.8)

This invention relates to a method for preparing halogenated maleic acid, salts and anhydrides thereof from octahalocycloheXene-3-one-l and more particularly relates to a method for preparing dihalcmaleic acid, salts and anhydrides thereof by scission of octahalocyclohex- ,ene-B-one-l in the presence of a strong alkali.

Dichlorog dibromoand chlorobromomaleic acids and anhydrides are useful for preparing copolymers with vinyl alkyl ethers such as methyl vinyl ether. The imides of the dihalomaleic acids mentioned above are useful as insecticides and herbicides.

An object of this invention is the provision of a method for preparing dihalomaleic acids, anhydrides and salts thereof from octahalocyclohexene-3one-l. Another object is the provision of a method for the preparation of dichloromaleic acid, salts and anhydrides thereof by scis- Sion of .octachlorocyclohexene-3-one-l in the presence of a strong alkali. Another object is the provision of a method for preparing dibromomaleic acid, salts and anhydrides thereof by scission of octabromocyclohexene-3- one-l in the presence of a strong alkali. Still another object is the provision of a method for preparing chlorobromomaleic acid, salts and anhydrides thereof by scission of an octahalocycloheXene-3-one-1 which has both chlorine and bromine atoms on adjacent carbon atoms of the cyclohexeue ring, preferably in either the 3 or 4 position. Numerous other objects will be apparent from the following description which discloses a preferred embodiment of the invention.

These objects are accomplished by splitting an octahalocyclohexene-3-one-l ring with a strong alkaline material.

Included among the strong alkalies which are useful for effecting this scission are lithium, sodium, potassium and cesium hydroxides, oxides, carbonates and bicarbonates. In addition, the alkaline earth metal hydroxides are sufiiciently alkaline to cause a rupture of the ring and yield dihalomaleic, acids, salts and anhydrides.

The octahalocyclohexene-3-one-1 can be prepared by exhaustive chlorination or bromination of phenols or partially halogenated phenols preferably in the presence of a chlorination catalyst such as ferric chloride or SbCl and in the presence of actinic light. This exhaustive halogenation of phenol yields a mixture of octahalocycloheXene-3-one-1 and octahalocyclohexene-Z-one-1. In order to prepared the dihalomaleic acids, salts or anhydrides thereof it is not necessary to purify the octahalocyclohexenones at this stage, since each of these cyclic halogenated ketones yields a different end product upon alkaline scission of the cyclohexene ring and therefore separation can be made after treatment with a strong alkali. Alternatively, it is possible to separate the two octahalocyclohexenone compounds and treat only the octahalocycloheXene-3-one-1 with the alkaline material to form the maleic compounds directly. Because of the alkalinity of the reacting medium salts of dihalomaleic acid are usually formed with inorganic alkaline compounds. The dihalomaleic salts can be readily converted ice to the acids by acidification and thereafter heating above the melting point to convert the acid to the anhydride.

The octa-halocyclohexene-3-one-1 compounds that can be reacted With strong alkaline materials to form the dihalomaleic acids include 2,2,3,4,5,5,6,6-octachlorocyclohexene-3-one-l, 2,2,3,4,5,5,6,6-octabrornocyclohexene- 3-one-1, 2,2,4,5,5,6,6-heptachloro-3-bromo-octahalocyclohexene-3one- 1 2,2,3 ,5 ,5 ,6,6-heptachloroA-bromo-cyclohexene-S-one-l. It is evident that other octahalocyclohexene-3-one-1 compounds can also be employed, for example, the octahalocyclohexene-B-one-l which results from halogenation of phenol or a partially halogenated phenol by a mixture of chlorine and bromine can be used. Also a compound such as a 2,4,6-trichloro phenol can 'be brominated to form 2,3,5,5,6-pentabromo-2,4,6-trichlorocyclohcXene-3-one-1 or 2,4,6-tribromo phenol can be chlorinated to yield 2,3,5,5,6-pentachloro-2,4,6-tribromo cyclohexene-3-one-1. In the latter two cases the maleic acid or its derivative that results from the scission of the cyclohexene ring by alkali will contain both chlorine and bromine in its final structure.

A strong alkaline material is essential for splitting the octahalocyclohexene-3-one-1 molecule. The reaction will proceed very slowly at room temperature or below, but it proceeds with increased rapidity as the reaction temperature is increased and for that reason a reaction with an alkali metal hydroxide at a temperature of 60 C. or higher is preferred. Refluxing the reactants will cause the reaction to go to completion within a few hours. The reaction can occur in the presence of a diluent such as water, dioxane, acetone or other liquid organic media in which the alkali is soluble and with which the alkali does not react.

The following examples are intended to be illustrative and are not to be construed as a limitation on the invention. The parts are by weight unless otherwise expressly indicated.

Example 1 Three parts of 2,2,3,4,5,5,6,6-octachlorocyclohexene-3- one-1 .were reacted with 20 parts by volume of 20% aqueous sodium hydroxide at 60 C. for 24 hours. The reaction mixture was filtered and the filtrate was acidified with hydrochloric acid. After acidification the filtrate was extracted with ether and the ether was thereafter evaporated. 1.1 parts of a solid remained. This solid had a melting point of to C. A portion of this material was sublimed and the sublimate had a melting point of 114 to 117 C. The structure of this end product was proven to be that of dichloromaleic anhydride. Fusion of the sublimate with urea at 110 C. yielded a solid with a melting point of 174 to 175 C. which agrees well with that reported for dichloromaleimide. The yield of dichloromaleic acid based on the octachlorocyclohexenone reacted is equal to about 74%.

Example II Exhaustively chlorinated phenol was employed in this example. The initial starting material contained a mixture of 2,3,4,4,5,5,6,6-octachlorocyclohexene-2-one-1 in an amount of about 40% by weight and 2,2,3,4,5,5,6,6- octachlorocyclohexene-3-one-l in an amount of about 60% by weight of the mixture. To parts of this mixture of octachlorocyclohexenones were added about 900 parts by volume of 2 N sodium hydroxide at 5 to 10 C. This mixture was allowed to come to room temperature slowly and was stirred for 4 days. A slight amount of unreacted material remained in suspension. The solids were separated from the liquid by filtration and washed with cold water. The filtrate was acidified and extracted with ether to yield 49 parts of dichloromaleic acid. This was sublimed under vacuum to yield 29.8 parts of dichloromaleic anhydride having a melting point of 115 to 118 C.

Example Ill It is possible to take a mixture of octahalocyclohexene- 2-one-1 and octacyclohexene-3-one-1 and react the former preferentially in the presence of a weak alkali to convert it to an aliphatic derivative and thereafter react the octa- -halocyclohexene-3-one-1 with a strong alkali without previously separating the reaction ingredients. 250 parts of a mixture of octachlorocyclohexene-2-cne-1 and octachlorocyclohexene-S-one-1 in which the latter was present in a proportion of about 60% by weight were treated with 400 parts of anhydrous sodium acetate in 600 ml. of dioxane and 1000 ml. of methanol, by refluxing the mixture for about six hours. This reaction mixture was poured onto chopped ice and an oil in an amount of about 212.7 parts separated. On cooling the dried oil crystals were formed. These crystals were separated by filtration and were found to be unreacted octachlorocyclohexene-3-one-l. The oil filtrate contained approximately 25 to 40% by weight of unreacted octachlorocyclohexene-3-one-l. 22.8 parts of the oil were treated with an excess of 2 N NaOH and the mixture was stirred at room temperature for five days. In the alkaline medium the sodium salt of hepta'chlorohexadienoic acid settles as a solid. This is removed by cooling and filtration. The

filtrate on acidification and extraction yields dichloromaleic acid. Dichloromaleic anhydride was recovered by sublimation of the dichloromaleic acid. In this reaction it is believed that methyl heptachlorohexadiene- 2,5-oate is formed by the reaction of sodium acetate and methyl alcohol with octachlorocyclohexene-2-one-1 as demonstrated by conversion of the ester to the free acid. Under the reaction conditions the octachlorocyclohexene- 3-one-1 is stable to the alkali metal salts of the weak acid. It is possible to separate octahalocyclohexene-3-one-1 from the methyl ester of heptahalohexadiene-2,5-oic acid and then to react the purified octahalocyclohexene-B- one-1.

Another means for purifying octahalocyclohexene-3-one-1 is by the reaction of the mixture with sodium acetate in acetic anhydride. Under these reaction conditions pentahalophenol acetate is formed from the octa- 4 presence of strong alkali will take place. The temperature at which the above halogenated maleic derivatives are formed can vary from about 0 C. to that of the reflux temperature since the end products are relatively stable and reaction rate is much faster at the elevated temperatures.

The methods described in this invention provide a very simple and easy method for preparing dihalomaleic acids, salts and anhydrides thereof in very good yield of or better.

Although I have explained the invention by reference to specific examples it is believed apparent that many variations can be made in the conditions, the proportions of reacting ingredients and other modifications without departing from the spirit and scope of the invention except as defined in the appended claims.

I claim:

1. A method of preparing salts of dihalomaleic acid comprising reacting an octahalocyclohexene-3-one-1 with an excess of an alkali selected from the class consisting of alkali metal hydroxides, oxides, carbonates and bicarbonates and alkaline earth metal hydroxides in an inert diluent at a temperature ranging from about room temperature to the reflux temperature of the mixture until scission of the cyclohexenone nucleus is effected, the halogen in said maleic acid salts and said octahalocyclohexene-3-one-1 being selected from the class consisting of chlorine and bromine.

2. The method of claim 1 in which the alkali is sodium hydroxide.

3. The method of claim 1 in which the alkali is potassium hydroxide.

4. The method of claim 2 in which octachlorocyolohexene-S-one-l is reacted. i

5. The method of claim 2 in which octabromocyclO- hexene-3-one-1 is reacted.

6. The method of claim 1 in which the octahalocyclohexene-3-one-1 has at least 1 chlorine atom and at least one bromine atom on the carbon atoms in the 3 and4 positions of the octahalocyclohexene-3-one-1 molecule.

7. The method of claim 1 in which the temperature is between about 60 C. and the reflux temperature of the reaction mixture.

8. The method of claim 1 in which the reaction mixture is acidified upon completion of the conversion reaction thereby forming a dihalomaleic acid.

9. The method of claim 8 in which the dihalomaleic acid is heated above its melting point to cause sublimation of the dihalomaleic anhydride.

References Cited in the file of this patent UNITE STATES PATENT OFFICE CERTIHQATE 0F CORRECTED Patent Noo 2,843,606 July 15, 1958 iiharlos PQJCIIliIlO Column 1, line 60 for "preepared" read prepare column 2, line: l4, striko out "a'"n geoond occurrence; column 3, line 23, for "2208" read 2308 o Signed and sealed this 16th day of December 1958a (SEAL) Attest:

KARL Ho AXLINE ROBERT C. WATSON Attesting Ofi lcer Commissioner of Patents 

1. A METHOD OF PREPARING SALTS OF DIHALOMALEIC ACID COMPRISING REACTING AN OCTAHALOCYCLOHEXENE-3-ONE-1 WITH AN EXCESS OF AN ALKALI SELECTED FROM THE CLASS CONSISTING OF ALKALI METAL HYDROXIDES, OXIDES, CARBONATES AND BICARBONATES AND ALKALINE EARTH METAL HYDROXIDES IN AN INERT DILUENT AT A TEMPERATURE RANGING FROM ABOUT ROOM TEMPERATURE TO THE REFLUX TEMPERATURE OF THE MIXTURE UNTIL SCISSION OF THE CYCLOHEXENONE NUCLEUS IS EFFECTED, THE HALOGEN IN SAID MALEIC ACID SALTS AND SAID OCTAHALOCYCLOHEXENE-3-ONE-1 BEING SELECTED FROM THE CLASS CONSISTING OF CHLORINE AND BROMINE.
 8. THE METHOD OF CLAIM 1 IN WHICH THE REACTION MIXTURE IS ACIDIFIED UPON COMPLETION OF THE CONVERSION REACTION THEREBY FORMING A DIHALOMALEIC ACID.
 9. THE METHOD OF CLAIM 8 IN WHICH THE DIHALOMALEIC ACID IS HEATED ABOVE ITS MELTING POINT TO CAUSE SUBLIMATION OF THE DIHALOMALEIC ANHYDRIDE. 